Story below about Chicago's ghost bike issue, where friends and family of fallen cyclists put up a stripped bike, painted white to signify a cyclist's death. Some neighbors (rightfully in my mind) wonder when it should be removed rather than left to disintegrate on its own. Families and friends, however do not share that idea.
The idea of permanent memorials for regular people has never been resolved as far as I know in any city or town. You pass the highway memorials put up by families and we certainly have some left from the federal levee breaks, especially those homeowners who have left their X as a permanent reminder but the public space is left for war and public officials memorials only.
The idea of using ghost bikes as a reminder of a bicycle death seems appropriate given the war between cyclists and those in tanks disguised as cars. Maybe the answer is a ghost bike which is then replaced after a period by a sticker or metal sign naming the person and date and time of the accident to be left as a reminder of the danger as well.